[clang] [llvm] [RISCV][MC] Add experimental Smidctrl, Ssidctrl, Smnip, and Ssnip support (PR #218108)

[Sam Elliott via llvm-commits]

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@@ -113,15 +113,9 @@ Makes programs 10x faster by doing Special New Thing.
 
 ### Changes to the RISC-V Backend
 
-* Added experimental MC support for the `Smcsps` and `Sscsps`
-  conditional stack pointer swap extensions.
+* Added experimental MC support for the ACLIC v0.20 extensions.
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lenary wrote:

Can you list all the affected extensions in the single release bullet point? It makes it a lot easier to grep the release notes through several branches to find out when something appeared.

https://github.com/llvm/llvm-project/pull/218108